Process for preparing fluorinated C4 to C6 hydrocarbons and novel cyclic fluorinated hydrocarbons and their use as propellant gas and working fluid for heat pump systems

ABSTRACT

This invention relates to a process for preparing fluorinated C 4  to C 6  hydrocarbons by catalytically hydrogenating, in the presence of a base, at least partially halogenated olefins. This invention also relates to certain novel cyclic fluorinated C 5  and C 6  hydrocarbons prepared by the process of this invention. This invention further relates to the use of fluorinated C 4  to C 6  hydrocarbons as propellant gas or as working fluid for heat pump systems.

This application is a division of application Ser. No. 07/257,351 filedOct. 13, 1988, now U.S. Pat. No. 4,902,839

BACKGROUND OF THE INVENTION

The present invention relates to the preparation of linear and cyclicfluorinated C₄ to C₆ hydrocarbons by catalytic hydrogenation ofappropriate haloolefins, to novel cyclic fluorinated hydrocarbons, andto the use of fluorinated C₄ to C₆ hydrocarbons as propellant gas andworking fluid for heat pump systems.

Processes for preparing special fluorinated C₄ hydrocarbons are known.Thus, 1,1,1,4,4,4-hexafluorobutane can be prepared by reacting succinicacid with sulfur tetrafluoride. W. Dmowski et al, PL Inventor'sCertificate 87,481. This process is unsatisfactory since it requiressulfur tetrafluoride, which is not only toxic but is accessible only byan uneconomical method. 1,1,1,4,4,4-Hexafluorobutane can also beprepared by hydrogenating 1,1,1,4,4,4-hexafluoro-2-chloro-2-butene or1,1,1,4,4,4-hexafluoro-2,3-dichloro-2-butene catalytically in thepresence of palladium on aluminum oxide (Y. Huang et al, Youji Huaxve,2, 125 (1984)), but the product of this process is always obtained inthe form of mixtures with chlorine-containing compounds. However,according to more recent reports (see J. F. D. Mills, Cell. Polym., 5,343 (1987) and F. S. Rowland et al, Nature, 249, 0 (1974), the chlorinecontained in conventional propellant gases causes damage to the ozonelayer of the earth's atmosphere. Finally, 1,1,1,4,4,4-hexafluorobutanecan also be prepared by hydrogenation of1,1,1,4,4,4-hexafluoro-2-butene. R. N. Haszeldine, J. Chem. Soc.,2504(1952). The disadvantage of this process is that a difficultyobtained and expensive starting material must be used. R. N. Haszeldine,J. Chem. Soc., 2504 (1952).

1,1,2,2-Tetrafluorocyclobutane can be prepared by reaction oftetrafluoroethylene with ethylene in a "two+two" addition. D. Coffman etal, J. Amer. Chem. Soc., 71, 490 (1949). However, the yield of thisreaction is not satisfactory.

SUMMARY OF THE INVENTION

The present invention relates to a process for preparing fluorinated C₄to C₆ hydrocarbons of the formula (I) ##STR1## wherein R_(f) is CF₃ orthe two R_(f) groups taken together are --CF₂ --CF₂ --, --CF₂ --CF₂--CF₂ --, or --CH(CF₃)--CH(CF₃)--,

comprising catalytically hydrogenating, in a presence of suitable base,olefinic compounds of the formula (II) ##STR2## wherein X is hydrogen,fluorine, chlorine, or bromine;

Y is fluorine, chlorine, or bromine: and

R_(f) has the meaning given under the formula (I).

DETAILED DESCRIPTION OF THE INVENTION

Suitable olefinic compounds of the formula (II) of this inventioninclude, for example, 1,1,1,4,4,4-hexafluoro-2-chloro-2-butene,1,1,1,2,4,4,4-heptafluoro-2-butene,1,1,1,4,4,4-hexafluoro-2,3-dichloro-2-butene,3,3,4,4-tetrafluoro-1-chlorocyclobutene,3,3,4,4-tetrafluoro-1,2-dichlorocyclobutene,3,3,4,4,5,5-hexafluoro-1-chlorocyclopentene,3,3,4,4,5,5-hexafluoro-1,2-dichlorocyclopentene,3,4-di(trifluoromethyl)-1-chlorocyclobutene,3,4-di(trifluoromethyl)-1,2-dichlorocyclobutene,1,1,1,4,4,4-hexafluoro-2,3-dibromo-2-butene and1,1,1,4,4,4-hexafluoro-2-bromo-3-chloro-2-butene.

It is not absolutely necessary to start with olefinic compounds of theformula (II). It is also possible to start with precursors which givecompounds of the formula (II) as intermediates. Precursors of compoundsof the formula (II), can be, for example, compounds of the formula (III)##STR3## wherein each X and each Y independently of one another andR_(f) have the meaning given under the formula (I) or (II). Thecompounds of the formula (III) can be converted to compounds of theformula (II), for example, by elimination of hydrogen halide. Ifdesired, such an elimination reaction can be preceded by the exchange ofhalogen for hydrogen. Examples of compounds of the formula (III) include1,1,1,4,4,4-hexafluoro-2,2,3-trichlorobutane,1,1,1,4,4,4-hexafluoro-2,2,3,3-tetrachlorobutane and1,1,1,4,4,4-hexafluoro.2,3 dibromo-2-chlorobutane.

Preferred starting compounds used in the process according to theinvention include the following compounds of the formula (II):1,1,1,4,4,4-hexafluoro-2-chlorobutene,3,3,4,4-tetrafluoro-1,2-dichlorocyclobutene,3,3,4,4,5,5-hexafluoro-1,2-dichlorocyclopentene and1,1,1,2,4,4,4-heptafluoro-2-butene.

The starting compounds for the process according to the invention arereadily accessible, using, for example, the method according to GermanOffenlegungsschrift 3,725,013, or H. L. Henne et al, J. Am. Chem. Soc.,67, 1235 (1945), and 73, 1103 (1951).

Suitable hydrogenation catalysts for the process according to theinvention include metals or metal-containing materials. Suitableexamples include the metals of transition group VIII of the periodictable of the elements, especially palladium, platinum and nickel. Themetals can be used in elemental form or in the form of compounds (forexample, as oxides or hydroxides). The metals can also be used inspecially activated forms, for example, in the form of Raney metals, orapplied to a carrier material. Preference is given to Raney nickel orpalladium on carbon, aluminum oxide, silica, barium sulphate, calciumcarbonate, lithium aluminum spinel, silica gel or magnesium oxide. It isalso possible to use catalysts which contain two or more metals, forexample nickel and iron. The catalysts can also be doped with additivesin any desired manner.

In general, the amount of catalyst is not critical. For example, 1 to100% by weight of catalyst, based on the compound of the formula (II)used, can be used. The quantity of catalyst refers to the catalyticallyactive component of the catalysts, so that if supported catalysts areused, the weight of the carrier material is not included whencalculating the amount of catalyst to be used.

Suitable bases for the process according to the invention include a widerange of inorganic and organic alkaline compounds. Examples of suchbases include the oxides, hydroxides, acetates, carbonates andbicarbonates of alkali metals and alkaline-earth metals, as well astertiary amines. Preferred bases include potassium hydroxide, sodiumhydroxide, sodium acetate, triethylamine, and pyridine.

The bases can be used in various amounts. If compounds of the formula(II) in which X is hydrogen are used, 0.8 to 1.2 equivalents of base permol of the compound of the formula (II) are preferably used. Ifcompounds of the formula (II) in which X is chlorine are used, 1.8 to 3equivalents of base per mol of the compound of the formula (II) arepreferably used.

The hydrogenation according to the invention can be carried out atvarious pressures and temperatures. Suitable pressures are, for example,those in the range of about 1 to 200 bar and suitable temperatures arethose in the range of about 0 to 200° C. Preference is given topressures in the range of about 1 to 60 bar and to temperatures in therange of about 20 to 60° C.

The process according to the invention is preferably carried out in thepresence of a solvent. Suitable solvents include, for example, alcoholssuch as methanol and ethanol, ethers such as tetrahydrofuran anddiglyme, aromatics such as toluene, and alkanoic acids such as aceticacid.

The process can be carried out not only batchwise but also continuously.In the case of continuous operation, the catalyst is preferably arrangedin a fixed bed.

The reaction mixture can, for example, be worked up by first removingany solids present and then stripping the solvent from the filtrate. Itcan also be worked up by pouring the reaction mixture freed from thecatalyst onto ice water, separating the resulting organic phase, andthen fractionally distilling the organic phase. The reaction mixture canalso be worked up by any number of other methods known in the art.

The process according to the invention has several advantages. Forexample, the process requires no starting materials and reagents whichare difficult to obtain, it affords pure products in good yield, and itprovides an economical route to fluorinated, but chlorine-free,hydrocarbons.

The present invention further relates to novel cyclic fluorinatedhydrocarbons of the formula (Ia) ##STR4## wherein the two R_(f) groupstaken together are --CF₂ --CF₂ --CF₂ --or --CH(CF₃)--CH(CF₃)--: that is,1,1,2,2,3,3-hexafluorocyclopentane and1,2-di(trifluoromethyl)cyclobutane. A process for preparing the novelcompounds of the formula (Ia) is described above and possibilities forindustrial use are described below.

The present invention further relates to the use as propellant gas ofcompounds of the formula (I) ##STR5## wherein R_(f) is CF₃ or the twoR_(f) groups taken together are --CF --CF₂ --CF₂ --CF₂ --or--CH(CF₃)--CH(CF₃)--.

Preferably, these compounds can be used as propellant gas for sprayshaving a wide range of uses, for example, as sprays for cosmeticpurposes (such as deodorant sprays). Particularly preferably, thesecompounds can be used as propellant gas in sprays used for medicalpurposes, for example, in sprays for asthmatics or in liquid plastersprays. For such uses, particular preference is given to1,1,1,4,4,4-hexafluorobutane.

Sprays which, according to the present invention, contain compounds ofthe formula (I) as propellant gas are inert and nonflammable, as are thefluorinated and chlorinated hydrocarbons which hitherto have frequentlybeen used for this purpose. However, because the compounds of formula(I) are chlorine-free, these compounds have the additional advantage ofleaving virtually unaffected the ozone layer of the earth's atmosphere.

The present invention also relates to the use as working fluid for heatpump systems of compounds of the formula (Ib) ##STR6## wherein R_(f) "is CF₃ or the two R_(f) " groups taken together are --CF₂ --CF₂ --CF₂ or--CH(CF₃)--CH(CF₃)--.

The present invention, which is set forth in the foregoing disclosure,is not to be construed or limited either in spirit or in scope by theseexamples. Those skilled in the art will readily understand that knownvariations of the conditions and processes of the following preparativeprocedures can be used. In the following examples, all percentages arepercentages by weight and all temperatures are degrees Celsius unlessotherwise noted.

EXAMPLES Example 1

In a stainless steel autoclave, 40 g of1,1,1,4,4,4-hexafluoro-2-chloro-2-butene in 300 ml of ethanol werehydrogenated with hydrogen in the presence of 12 g of potassiumhydroxide and 25 g of Raney nickel for 3 hours at 20° C. and another 1hour at 100° C. at a pressure of from 30 to 40 bar. The solid componentswere then removed from the reaction mixture by filtration and theremaining liquid was distilled to give 16 g of1,1,1,4,4,4-hexafluorobutane having a boiling point of 25-30° C. at 1013mbar. The mass spectrum showed a molecular ion at m/e 166.

Example 2

199 g (1 mol) of 1,1,1,4,4,4-hexafluoro-2-chloro-2-butene werehydrogenated in 800 ml of diglyme in the presence of 45 g of sodiumhydroxide and 30 g of Raney nickel in the temperature range from 20 to40° C. and at a hydrogen pressure of 20 to 40 bar. The solid componentswere filtered off, the solvent was extracted with water, and the organicphase was separated and purified by fractional distillation. The yieldof 1,1,1,4,4,4-hexafluorobutane was 125 g (75% of theory). The boilingpoint was 24-27° C. at 1013 mbar. The ¹⁹ F-NMR spectrum showed one peakat -10.7 ppm (CF₃ CO₂ H standard).

Example 3

10 g (36 mmol) of 1,1,1,4,4,4-hexafluoro-2-bromo-3-chloro-2-butene werehydrogenated in 50 ml of tetrahydrofuran in the presence of 3.0 g ofsodium hydroxide and 5 g of Raney nickel in the temperature range from20 to 40° C. and at a hydrogen pressure of 20 to 40 bar. The reactionmixture was worked up as described in Example 2. The yield was 3.5 g of1,1,1,4,4,4-hexafluorobutane (59% of theory).

Example 4

40 g (0.2 mol) of 1,1,1,4,4,4-hexafluoro-2-chloro-2-butene werehydrogenated in 300 ml of ethanol in the presence of 12 g of potassiumhydroxide and 24 g of Raney nickel in the pressure range of from 20 to40 bar and at a temperature from 20 to 100° C. The solid components werefiltered off, the solvent was extracted with water, and the organicphase was separated and purified by distillation to give 15.5 g (47% oftheory) of 1,1,1,4,4,4-hexafluorobutane. The boiling point was 25 to 27°C. at 1013 mbar.

Example 5

50 ml of tetrahydrofuran, 8.5 g of sodium hydroxide and 3 g of 5% byweight palladium on carbon catalyst were added to 23.5 g (0.1 mol) of1,1,1,4,4,4-hexafluoro-2,3-dichloro-2-butene. This mixture washydrogenated with hydrogen at temperatures between 20 and 40° C. and atpressures in the range 20 to 40 bar. The reaction mixture was worked upas described in Example 2. The yield was 8.0 g (75% of theory) of1,1,1,4,4,4-hexafluorobutane.

Example 6

In a 1.3 l stainless steel autoclave, 245 g (1 mol) of1,2-dichloro-3,3,4,4,5,5-hexafluorocyclopentene were hydrogenated at 60to 70° C. with the addition of 202 g (2 mol) of triethylamine in 200 mlof methanol and in the presence of 20 g of Raney nickel. Over a periodof 12 hours, the theoretical amount of hydrogen was absorbed at ahydrogen pressure of 40 to 50 bar. The reaction mixture was filtered andthe methanolic solution was diluted with 400 ml of water. The lowerorganic phase was separated, washed with 100 ml of 5% aqueoushydrochloric acid, and dried over sodium sulfate. Distillation through a1-m spinning band column gave 106 g (60% of theory) of1,1,2,2,3,3-hexafluorocyclopentane having a boiling point of 87-88° C.at 1013 mbar. The mass spectrum showed the molecular ion at m/e 178.

n_(D) ²⁰ : 1.309

¹ H-NMR (internal TMS standard): 2.25-2.5 ppm (m, 4H)

¹⁹ F-NMR (external CF₃ COOH standard): 36.5 ppm (tt, 4 F) and -57.9 ppm(m, 2F)

What is claimed is:
 1. A compound of the formula ##STR7## wherein thetwo R_(f) ' groups taken together are --CF₂ --CF₂ --CF₂ --orCH(CF₃)--CH(CF₃)--.
 2. A compound according to claim 1 which is1,1,2,2,3,3-hexafluorocyclopentane.
 3. A compound according to claim 1which is 1,2-di(trifluoromethyl)cyclobutane.